“The bodhi-mind (bodhicitta) is its cause, compassion (karuṇā) is its root, and expedient means (upāya) is its culmination.”

Bodhicitta is understood both in the sense of the aspiration for enlightenment, as well as in the sense of one's potential for awakening, or Buddha-nature (relevant to any Dzogchen students reading this).

That's one practical aspect. There are other ways to explain it too. The whole of the Mahavairocana Sutra is here: